Spin—Orbit Coupling and Electron-Affinity Determinations from Radiative Capture of Electrons by Oxygen Atoms

Abstract

The radiative capture continuum for the process O⁰+e→O⁻+hν is studied in the region of the threshold, 7800–8800 Å. The spectrum is produced in shock‐heated vapors of potassium peroxide and rubidium oxide in neon and argon. Individual thresolds are resolved which correspond to the transitions $\mathrm{O}{(}^3{P}_2\mathrm{)\to }{\mathrm{O}}^{-}{(}^2{P}_{\frac{1}{2}}\mathrm{),}\mathrm{O}{(}^3{P}_2\mathrm{)\to }{\mathrm{O}}^{-}{(}^2{P}_{\frac{3}{2}}\mathrm{),}\mathrm{O}{(}^3{P}_1\mathrm{)\to }{\mathrm{O}}^{-}{(}^2{P}_{\frac{3}{2}})$ , and possibly $\mathrm{O}{(}^3{P}_0\mathrm{)\to }{\mathrm{O}}^{-}{(}^2{P}_{\frac{1}{2}})$ . From these thresholds, the electron affinity of the oxygen atom is determined to be 1.478±0.002 eV and the separation of ${}^2{P}_{\frac{1}{2}}{,}^2{P}_{\frac{3}{2}}$ states of O⁻, 285±15 cm⁻¹, corresponding to a spin—orbit coupling constant of 190±10 cm⁻¹ for the oxygen negative atomic ion.